Fast UART

Memec Design

February 25, 2003

3

Optimized for

Functional Description

Structure of UART-F

The structure of MC-ACT-UARTF consists of four principal block. A dual advanced high speed baudrate synthesizer

is implemented to serve as receiver sampling source and transmitter clock source. Clock generation is configured

through 16-bit register value.

Format analyzer detects the incoming data stream to sequence bits stored and interface by receive unit. The

detection and derivation of data stream enables a bit sampling mechanism to reduce necessary clock cycle in

receiving unit.

Transmit unit is starting serial out after a parallel event controlled interface is used.

Figure 2: UART-F Structure

Event Communication

For communicating events, the MC-ACT-UARTF core uses or produces active ‘1’ pulses, which are activated for

only one clk cycle. In the inactive state, they remain low with respect to the rising clk edge, so glitches may occur.

For communicating over clock domains, these events must be synchronized first!

Configuration

The configuration pins are used to set the bitrate, bit timing and output format. They’re static inputs and used for

both receiver and transmitter in common.

Baudrate

The baudrate generator is not a simple prescaler, but allows generating all baudrates from the system clock within a

certain range. There is no special clock frequency needed for that purpose so that you’re free to choose the system

clock for the MC-ACT-UARTF, which simplifies considerably the clock structure.

To configurate the baudrate a 16bit configuration register value is used.

Examples:

For 1Mhz clock and 115’200bps, n is 30198(dec), accuracy better than 33ppm,

For 20Mhz clock and 1Mbps, n is 13107(dec), accuracy better than 76ppm.

Limitations:

Values for n lower than 100(dec) should not be used, otherwise the accuracy may be below 1%.

e.g. for 1MHz clock, the possible baudrates with accuracy better than 1% range from 381bps to 250kbps.

RX Data

RX Ctrl

TX Data

TX Ctrl

serial out

Dual Advanced Hi Speed

Baudrate Synthesizer

Receive

Unit

Format

Analyzer

Transmit

Unit

Config

serial in

UART-F